Oximeter



June 2, 1953 M. D. LlsToN 2,640,389

ATTO R N EYS M. D. Lls'roN June 2, 1953 OXIMETER 2 Sheets-Sheet 2 Filed Oct. 31, 1950 f w .N5

INVENTOR BY /Mf @amm-wm ATTORNEYS Patented June 2, 1953 OXIMETER Max D. Listoni, Darien, Conn., assignor to The Perkin-Elmer Corporation, Glenbrook, Conn., a ycorporation of New York f .l Application October 31, 1950, Serial No. 193,078

9 claims. '(01. fzs-14) This invention relates to colorimeters and is concerned more particularly with a novel colorimeter suitable for general analytic purposes and especially adapted for indicating and measuring changes in the color of a specimen. In one photocells doesv not pass through the same part form, the new instrument may be employed as an of the ear and thus an error in measurement oximeter for determining the amount of oxygen may be introduced because of diiferences in the in the blood, and such an instrument is of great blood distribution in front of the two photocells. value in surgery, where modern anaesthetics may Finally, differences in results are obtained behave bad effects, if the oxygen tension of the pa- 10 cause of differences in the thickness and density tient is too low, and also in the study of various of the ears to be examined.

kinds of heart disease and respiratory ailments The present invention is, accordingly, directed frequently found in persons aiicted with polioto the provision of a novel calorimeter, which myelitis. The advantages of the invention are all measures the differential light absorption of a realized in such an oximeter and that embodisample and is not subjectvto the objections to ment of the invention will, accordingly, be illusprior similar instruments. In the newcolorimetrated and described in detail for purposes of exter, a single photocell is employed and the photoplanation. cell receives light from twosources passing al- It is well known that the color of the hemoternately along the same path through the speciglobin of the blood changes from red toward blue men. The output of the photocell is then passed with a decrease in the oxygen content and a numto an amplifier andY a synchronous detector, the ber of photo-electric methods for measuring the output of which passes to a meter showing the oxygen saturation of the blood, together with indifference in transmission of the light from the struments for practising such methods, have two sources. An oximeter constructed in accordheretofore been proposed and put into use to some ance with the invention includes a frame or ear extent. These instruments depend for their oppiece of C-shape, one end of which has va cavity eration upon the fact that, in the red region of containing the photocell disposed behind a transthe spectrum, reduced hemoglobin and oxyhemoparent window. The other end of the ear piece globin absorb diiferent amounts of light, so that is formed with a cavity containing the light changes in absorption of red light by the speci- 3o sources and closed by a window facing the winmen indicate changes in the oxygen content of dow in the other end of the frame. The light the specimen. sources are gas tubes, preferably electrode-less,

Typical oXimeters have been constructed hereand, if such electrodeless tubes are used, they toiore for examination of the ear iand they inare excited by radio-frequency elds. The end p clude an ear piece of. C-form, between the end-s of the ear piece containing the light sources is of which a part of the ear, such as the lobe, is provided with an adjustable sleeve, which can received. One end of the ear piece contains an be moved. to place a window at the end of the incandescent lamp Serving as a source of light,. sleeve in contact with the ear, and the window and the other end of the ear piece contains a may be covered by a transparent diaphragm, Pair 0f photocells lying Side by side behind re- 4o which can be inflated to squeeze blood out of the YSpective lters of diierent characteristics and ear tissue to be examined to secure a bloodless facing the source. The responses of the photoreading, by air under pressure admitted to the cells are then used for measuring the Oxygen COnsleeve and passing to the diaphragm through an tent of the blood in the ear. opening in the sleeve window.

Such prior oximeters suier from the disadvan- 4.5 For a better understanding of the invention, tage that every ear piece has its own characterreference may be made to the accompanying istic sensitivity and must be calibrated empiridrawings, in which: A cally. Calibration involves drawing and analyz- Figure. 1 is a view, partly in elevation and ing a large number of blood samples, so that it is partly yin section, -of a frame or ear piece of an extremely laborious and costly, since each analycximeter embodying the invention; sis may consume as much as three hours of the Fig. 2 is a sectional view on the line 2-2 of time of a skilled technician. Another disadvan- Fig 1; and tage arises from the fact that the color of the Fig. 3 is a circuit diagram of the oximeter. Y light emitted by the lamp is likely to vary over a The oximeter illustrated in the drawings comperiod of use and, whenever replacement of the prises an ear piece l0 of any suitable metal and of lamp is required, the ear piece must be re-cali- 2 brated. Similar diiiiculties ensue from a lack of uniformity in the photocells and, filters used. Another serious disadvantage of the prior instruments is that the light falling upon the two C-shape, vand one end I'I of the ear piece has a cavity, within which is mounted a photocell I2. The inner side of the cavity is closed by a transparent window I3.

The other end of the ear piece carries a chamber Ill, generally cylindrical in form and disposed with its axis aligned with photocell I2. 'I'he chamber `I liispreferably--madehofvan. insulating material, suchf as asuitable plastic,fand.ring electrodes I5, I6, I'I are embedded in the wall of the chamber and connected to leads (5a, IGa, and..

I'Ia, respectively, which extend through a passage I8 in the wall of the chamber, to the exterior The ring electrodesesupport.acpair of.. electrode-less gas tubes I9, 2G, of-whichtube-.lis

thereof.

lled with neon and tube 2!! contains argon. Each tube has one end mounted in an outer electrode I5 or I'I and electrode IE serves'ffr botlrtub'es:` The inner end of chamber III is closed by aftransparent window 2 I without nltering eiect, but, for some purposes, ,the window fmayzltenout. light .of undesired wave lengths from' the two tubes. Also, a ilter may, be mounted 'within chamber I4 to iilterthelight from. the .outer source, .in this case,y

argon tube 25;" The position'of. the two tubesin chamber i4 is not Ycritical,although it 'is' preferable to. place' the. source emitting;v the light, 4to which the ,photocell gives the strongenresponse, in theouter positionnthat is,'farther VfromwindowZI.

A cylindrical sleeve22is` telescopedover chamber I4 and the -sleeve has 'an'eck'22a at its inner end the neck havingan innerdiameter approximately thesame as chamber M; The end ofthe neck is closediby 'a transparent window 23 having a central hole 'anda thintransparent rubber diaphragm '2 4" overlies Vthe window23 i'andis held' in place byhaving' its edge clamped against the outer surface of theneck'.' A' passage is formed inthe walls .of the neckand. the chamber, so that air under pressure maybe admittedithrough the interior of vthe neck to the under side Yoi thediaphragm to inflate it. The sleeve 22 'is adjustable along the outside of chamber. I4 and is held in adjusted lposition b'y aclamp. 26,`which' .islcarried by the sleeve andmay be forced against .the outside of the chamber byascrewfl'provided `with a wing nut 21a.

The wiring diagram, 3, shows that the instrumentA may, be operated by a 60`cycle' A. C.

source, which supplies..energy` to aD. C'. power. supply unit Zil'and. the primaries of modulation transformers 29, 3GLthe connections to theprimaries b'eirlgreversed.y Theunit 28, which'comprises an electronicrectier and a filter, is connected to one terminalof .eachl of theisecondari'es of .transformers 29,30, 'and the other terminals of the secondaries are connected .to respectiveradio-Y frequency, oscillators 3I,[32. The oscillators .sup-

ply radio frequencyenergy tothe .primaries of respective radio frequency Y. step-up transformers 33, 34, vthe secondaries of which are connectedy to the ring electrodes. I5;k I'l,-` while electrode I6 is grounded. The low level `signal from photocellll 2 passes to an amplier-.Sj receivingD'.' C. power from unit 28.' TheA. C.' output `from the amplifier represents the dirence in'. response of thev photocell to the light from the rtwo sources Vfalling thereon and the output is passed to asynchronous detector 35, receivingA. C. power from the secondary of atransformer..3'1;y theprimaryof which is connected to the 60 cycle A. C'. line. The output of the synchronous.. detector passes .as a i D. l C. signal to azmeter .38, which mayindicate :only or both. indicate .and..record.

In .the .useof .theioximeten .theear illeceisap- 75 plied to the lobe of the patients ear, and sleeve 22 of the ear piece is adjusted, so that the ear lobe is snugly engaged on opposite sides. Air under pressure is then admitted to inflate the diaphragm and cause it to exert pressure to squeeze the blood out of the tissue. The tubes I9, 20 are so operated-.that they-flicker in alternationiandpwith the tubes.thusf\operating, awreading. is taken- The meter shows the difference in absorption by the .fti-ssue of the red light from the neon tube and the infrared light from the argon tube. After the preliminary empty cell reading, the air pressure is released anda second-reading, taken after the bloodl has.retu1'ned.-.to the part of the lobe being yexamined, givesian-.indication of the oxygen content of the blood.

Inftheinstrument,A the co-axial mountings for theltubes, the walls of chamber I4, and the transparent Windows 2I and 23 cooperate to cause the light. from both.the red. and infrared sourcesto travel' along' paths" having; co-linear portions through* the specimen; anderrors; which" might arise from diiierences'in'the specimemif Lthe light" from the two 'sources haddiiierent -paths through* it; as inthe former instruments', i are, accordihglir, i

eliminated'.` The tubes are preferably' Without' electrodes, since this avoids variations in th'ecolor of the light emitted' as' a result of the gettering action 'of' electrodes'andthe'use of radio-fre` quen'cyA excitation for'such'tubes 'givesihi'gher in-A tensities and longer life;

The simple amplien'readin'gthe diierence between the transmittedJ red. and infrared' light gives -an approximate solutiorrof "thetheoreti'cal because `of the useof the oxygen bythe tissue and.

the zero readingv islthen that of thetissue, thetissue fluidQandthereduced blood.' The methodinvolvingtrapping, probably Vgives more accurate results.

The new oXimeter, inthe form .describedmay be employed ffor determining the .oxygen content of theblood uin the body of th'epatient, as, for. example', by; examining the lobe of the ear, the .web between two.fingers, etc., or. it may be usedfor. determining.. the Aoxygen .content .of :a: sample of arterialblooddrawn from the patient and placed..

in a sealed cell or cuvette.

I lclaim.:

l. In .anoximeten the combination. of awframe.' having a..pair .of mountings `spaced to receive 'a part of the body between them, apair of gas tubes in onemounting,` one of the tubes containing neon andtheother argon, awindow iii-:saidmounting,V

throughavhichlight fromthe tubespasses along the. same path .toward the. second mounting, a.v detector in. the` second mounting -in position. to

receive light from. the tubes,. which has-passed through the `part of the body, means for.exciting: the .tubes alternately, and measuring means receivingthe .output of thedetector and-measuring..

the difterence .in the .response Aof the detector to light vfrornthe Vtwotubes,v

2.- Anearlpiecefonuse in an.oximetercompris...v

ing a frame or G-shape, a chamber in each branch of the frame adjacent the yend thereof, windows at the opposed faces of the chambers, a pair of gas tubes producing light of dierent wave length-s mounted in alignment in one chamber and coaxial with the window of that chamber, and detecting means mounted in the second chamber in position to receive light from the tubes passing through the Windows.

3. A colorimeter, which comprises a pair of sources of light of different Wave lengths, means for causing light from the sources to travel along paths having co-linear portions, a detector lying at the end of the co-linear portions of the paths in position to receive light from the sources, the detector responding to light from the sources falling thereon, and the co-linear portions of the paths being of suicient length for insertion therein of a specimen to be examined, and means for operating the sources to cause them to flicker in alternation.

4. A colorimeter as defined in claim 3, in which the sources of light are gas tubes.

5. A colorimeter as defined in claim 3, in Which the sources `of light are gas tubes and the tubes are operated by radio frequency fields to cause them to ilicker in alternation.

6. A colorimeter as defined in claim 3, in which the sources of light are electrode-less gas tubes.

7. An oximeter, which comprises a frame having a pair of mountings spaced to receive a part of the body between them, a pair of sources of light of different wave lengths in the rst mounting, a Window in said first mounting through which light from the sources issues to travel along a single path from the Window to the second mounting, a detector in the second mounting in position to receive light from the sources along said path, and means for operating the sources to cause them to icker in alternation.

8. An oXimeter as dened in claim 7, in which the sources emit red and infrared light, respectively.

9. An oximeter, as dened in claim 7, in which the sources are gas tubes and the tubes are disposed in a line passing through the window and the detector.

MAX D. LISTON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,890,837 Whalen Dec. 13, 1932 2,217,991 Peck et al Oct. 15, 1940 2,241,743 Schoene May 13, 1941 2,256,855 Zobel Sept. 23, 1941 2,358,992 Millikan Sept. 26, 1944 2,382,439 Osborn Aug. 14, 1945 2,439,373 Stearns Apr. 6, 1948 2,442,462 Kirchbaum June 1, 1948 2,562,181 Frommer July 31, 1951 FOREIGN PATENTS Number Country Date 20,127 Australia Nov. 12, 1934 

